The invention relates to a flexible double-layered band of link members, in particular to a wristwatch strap.
In known bands or straps, the upper layer of link members are offset to the lower link members by half the width of the link members and are connected to each other by U-shaped clips which are inserted into the open end faces of the link members. The clips cooperate with leaf springs inserted in the link members.
Such flexible bands are extensively used since they have many advantages in comparison to closing bands. They can be easily put on or drawn off and do not clamp the wrist due to the elasticity and flexibility. Moreover, some of these band structures (for example DE No. 1,557,630) allow an adjustment of the length to the wrist of the user without any difficulty. Furthermore, these bands are relatively cheap since they can be essentially produced in an automatic manner.
Although this principle seems to be rather sound, these known constructions of flexible bands of link members have the disadvantage of relatively large dimensions. Especially when using bands in which the clips are locked with the leaf springs by means of corrugations or transverse grooves, like in the DE No. 896,757 or FR No. 1,554,048, this disadvantage is especially noticeable. The end latches require relatively much space so that the backlash required for stretching of the band is confined. Since the bands, however, should have a large stretching length, the height of the link members is considerable in order to enlarge the angle around which the shanks of the connecting clip are to be pivoted. Since the band has two layers of such link members, the height of such a band is correspondingly doubled.
Since years, the development of mechanical as well as electronic watches has been directed to structural units which are as flat as possible. Consequently, more and more flat wristwatch straps appeared on the market which harmonized with the height of the watch.
In order to reduce the height of such bands or straps, it has been proposed to develop the shanks of the connecting clips and the leaf springs in a smooth manner while the U-shaped clips are secured against falling out by end lugs formed onto the link members (DE No. 1,900,290). Although the entire height or thickness of such a strap is reduced, the adjustment to the length is rather complicated, since the lugs must be upwardly bent at the link members in order to insert or remove the link members from the band. Consequently, there is the danger that the lugs break off, and in any case the band is damaged after shortening at the respective location.
In addition, there are known numerous other modifications of flexible bands of link members. A satisfactory solution, however, for obtaining a very flat band of this kind and which possesses all the advantages thereof has yet to be found.